The present invention relates to battery-operated mobile radio stations, and more particularly, to balancing the desire to conserve battery power with other factors that effect mobile station performance.
Mobile communications have developed from first generation, analog-based mobile radio systems to second generation digital systems, such as the European Global System for Mobile communications (GSM). Current developments for a third generation of mobile radio communications are referred to as the Universal Mobile Telephone communications System (UMTS). In simple terms, the UMTS is xe2x80x9ccommunication to everyone, everywhere,xe2x80x9d where communication includes the provision of information using different types of media, i.e., multimedia communications. The goal of UMTS services is to combine both fixed and mobile services to form a seamless, end-to-end service for the user.
Because of the widespread success of the existing GSM platform, i.e., a global xe2x80x9cGSM-footprint,xe2x80x9d as well as the inherent upgradability and modularity of the GSM platform, there is a strong impetus to base the UMTS on an xe2x80x9cevolvedxe2x80x9d GSM platform. Accordingly, the present invention is described in the context of a UMTS based on an evolved GSM platform, and therefore, uses GSM terminology. Of course, the principles of the present invention are not limited to a UMTS, a GSM platform/terminology, or to any specific mobile communications network and may be implemented using other appropriate network platforms and configurations.
Current mobile/cellular telecommunications networks are typically designed to connect and function with Public Switched Telephone Networks (PSTNs) and Integrated Services Digital Networks (ISDNs). Both of these networks are circuit-switched networksxe2x80x94rather than packet-switchedxe2x80x94and handle relatively narrow bandwidth traffic. However, packet-switched networks, such as the Internet, are very much in demand and handle much wider bandwidth traffic than circuit-switched networks. While wireline communication terminals, e.g., personal computers, are capable of utilizing the wider packet-switched network bandwidth, wireless mobile radio terminals are at a considerable disadvantage because of the limited bandwidth of the radio/air interface that separates the mobile terminals from packet-switched networks.
There is also a need for a radio access system that provides wireless access at very high data rates and supports enhanced bearer services not realistically attainable with the first and second generation mobile communication systems. This need may be best satisfied by a Wideband-Code Division Multiple Access (W-CDMA) radio access network.
To assist in the following description, a UMTS 10 is now briefly described in conjunction with FIG. 1. A representative-connection-oriented, external core network, shown as the cloud 12, may be for example the Public Switched Telephone Network (PSTN) and/or the Integrated Services Digital Network (ISDN). A representative-connectionless-oriented, external core network, shown as cloud 14, may be for example the Internet. Both networks 12 and 14 are coupled to corresponding core network (CN) service nodes 16. The PSTN/ISDN circuit-switched network 12 is connected to a connection-oriented service node shown as a circuit-switched services node 18 which, in a GSM platform, includes a mobile switching center (MSC) 23 and a corresponding visiting location register (VLR) 24. Also in the existing GSM platform, the circuit-switched services node 18 is connected to a base station system (BSS) 26 which in turn is connected to a radio base station (BS) 28 having a corresponding geographical cell area 34.
The connectionless-oriented service node is a packet-switched services node 20 tailored to provide packet-switched type services. In the GSM platform, such a node corresponds to one or more of the General Packet Radio Service (GPRS) nodes, e.g., SGSN, GGSN, etc. Each of the core networks 18 and 20 also connects to a home location register (HLR) 22 which stores mobile station identification, subscription, and mobility/location information. Core network service nodes 18 and 20 are also connected to an UMTS radio access network (URAN) 30 which includes one or more radio network controllers (RNC) 32 coupled to one or more base stations 28, each base station having a corresponding geographical cell area 34. The radio access network 30 provides services to/from mobile stations 36 over the radio interface to the core network service nodes 18 and 20 without the core networks having to request specific radio resources necessary to provide those services. The UMTS radio access network (URAN) 30 xe2x80x9cmapsxe2x80x9d radio access bearers onto physical radio channelsxe2x80x94a task by and large controlled by the radio network controllers 32. In a W-CDMA system, individual radio channels are allocated using spreading codes. As described above, W-CDMA provides the wide bandwidth for multimedia services and other high rate demands. In addition, it also provides robust features like diversity handoff and RAKE receivers to ensure high communications quality.
When a mobile station is in an idle state, e.g., not involved in a connection with the URAN 30, the core networks need to be able to locate and communicate with the mobile station. Mobile stations also need to be able to initiate communications with the core networks. Typically, common channels are employed: one on the downlink direction from the base station to the mobile station (a paging channel), and another in the uplink direction from the mobile station to the base station (a random access channel). Periodically, the idle mobile station registers or otherwise makes its presence known to the base station of a particular cell in which it is currently physically located. If the core network service nodes do not know the specific cell where the mobile station is currently located, the core networks service nodes typically know the general location of the mobile station, i.e., a group of cells typically called a location area. Thus, when a call is to be directed from a core network to a mobile station, a paging procedure is performed where a paging message is sent to the mobile station over the downlink paging channel requesting that the mobile station initiate establishment of a connection with the radio access network 30 via the cell where it is currently located.
In order for the mobile station to receive paging messages, it must be xe2x80x9cawake,xe2x80x9d i.e., powered up, and listening at the appropriate time to the particular control channel over which the specific paging message was transmitted. If the mobile radio is continually powered and always monitoring that paging channel, there is a high probability that it will detect and accurately receive the page. But mobile stations are normally battery operated, and batteries have a limited life before they must be recharged. Continued monitoring of the paging channel therefore dramatically shortens battery life.
Accordingly, it is desirable to eliminate or otherwise minimize battery consumption where practical. The general idea is to place the mobile station into a low power consumption or xe2x80x9csleepxe2x80x9d mode to save battery power when the mobile station need not perform any necessary function. In order to make sure that it receives important messages, the mobile station is periodically awakened from its sleep mode to a higher power mode so that it can receive messages such as pages or send periodic updates of its location via a common channel. The basic problem of optimizing the sleep mode is a design tradeoff between a longer sleep mode which conserves the mobile station battery power and a shorter sleep mode which provides greater performance like faster call setup times or shorter data transfer delay in the downlink direction towards the mobile station.
One way to approach this optimization problem is to specify a fixed sleep mode period where all mobile stations experience the same battery consumption delay tradeoff. While this approach is attractive because of its relatively easy implementation and administration, it ignores among other things user preferences, priorities, and communications service requirements. It would be desirable to permit users to vary the sleep mode period to accommodate such preferences, priorities, and/or service requirements. Moreover, in situations where there is typically low mobile station activity, and where the mobile station location is known only generally rather than at an individual cell level, the fixed delay would need to be relatively long requiring a relatively long fixed sleep cycle. However, this longer period may be inappropriate for other services requiring shorter delays. As a result, the fixed sleep period would need to be set at a short sleep cycle to accommodate the highest activity mode and/or service tolerating the least delay. Thus, even though the mobile station may have a high activity level or use a short delay type of service for only brief intervals, the mobile station will wake up with high frequency all of the time. This high frequency wake up unnecessarily consumes limited battery power.
It is an object of the present invention to provide a power conserving sleep mode for a mobile station that may be varied to accommodate particular factors or circumstances.
It is an object of the present invention to provide a variable sleep mode where the mobile station initiates the change of the variable sleep mode.
It is a further object of the present invention to provide a variable sleep mode that takes into account different activity levels of the mobile station.
It is a further object of the present invention to provide a variable sleep mode that takes into account mobile station operator priorities and preferences.
It is a further object of the present invention to provide a variable sleep mode that takes into account different mobile station services and time constraints associated therewith.
It is yet another object of the present invention to coordinate variable sleep modes in mobile station communications with plural core networks.
The present invention solves these problems and meets these and other objects by providing a method of operating a mobile station where a sleep cycle of the mobile station may be optimally varied depending one or more conditions relating to the mobile station""s operation. Based on one or more of those conditions, a variable wake up parameter value is determined and used to establish times when the mobile station automatically leaves a lower power mode and enters a higher power mode to, for example, listen for a page. The mobile station""s variable wake up parameter is provided to the radio access network and to the core networks to permit coordination of communications and services with the mobile station.
If there is a change in one or more of the conditions that relate to the mobile station""s operation, the value of the variable wake up parameter may be varied in response to that change. For example, the mobile station may operate at plural activity levels and a detected change may include operating at a different one of the plural activity levels. The different activity levels have corresponding, different lengths of time required to setup a call or transfer downlink data. The detected change may also include the mobile initiating a change in an operating condition during the time the mobile is within one of those activity levels.
If the condition is the current activity level of the mobile station, the variable wake up parameter is varied to increase the frequency at which the mobile station wakes up for a higher activity level. For a lower current activity level, the variable wake up parameter may be varied to decrease the frequency at which the mobile station wakes up. If the condition is a service that is currently requested or subscribed by the mobile station, the variable wake up parameter value is varied to increase the frequency at which the mobile station wakes up if the current service requires a low delay. If the service permits a higher delay, the variable wake up parameter value may be varied to decrease the frequency at which the mobile station wakes up. If the service includes a maximum delay parameter, the value of the variable wake up parameter is varied to decrease the frequency in which the mobile station wakes up without exceeding that maximum delay parameter.
The present invention also permits a user to prioritize either battery conservation or lower delay, and as a result of that user priority, the variable wake up parameter is appropriately varied. Moreover, the variable wake up parameter value may also be varied depending on the type of power source currently powering the mobile station. For example, a power source having a shorter life suggests a longer sleep cycle; a power source having a longer life suggests the option of a shorter sleep cycle.
In a preferred example embodiment of the present invention, the wake up parameter is calculated in accordance with the following: S=2n, where S is the duration of the variable sleep cycle, measured for example as an integer number of communication channel frames, during which time the mobile station is in the lower power mode, and n is a variable integer. Assuming that the base station and mobile station communicate using a communications channel that is divided into a repeating sequence of M frames. The number of frames M in the sequence is preferably an integer power of 2. The specific wake up frame number W when the mobile station enters a higher power mode may be determined in accordance with the following: W=(kS) modulo M, where k is an integer.
The variable sleep mode approach of the present invention also provides considerable flexibility and optimization in communications networks such as the UMTS shown in FIG. 1. For each of the core networks, the mobile station may have a corresponding variable sleep parameter. As a result, the time interval when the mobile station awakens from a lower power sleep mode to a higher power sleep mode may vary based on the current operating conditions and communications between the mobile s station and the core networks. The present invention also provides a method of coordinating and synchronizing wake up time periods for plural core networks having different mobile station variable sleep mode parameters.
While the present invention does not eliminate the fact that there is a tradeoff between battery saving and service quality/delay, the variable sleep mode capabilities of the present invention permit optimization of that tradeoff in accordance with the individual objectives and/or conditions of a particular user/mobile station.